Sticky bonus
Bonus money that's yours to play but never to withdraw. It vanishes from your balance the moment you cash out.
A sticky bonus (also called non-cashable or phantom) is there to bet with, but at cashout the casino subtracts the bonus amount. Only the profit above it gets paid, usually once wagering's done.
Its opposite: the non-sticky bonus, nicknamed "parachute". Here, your real money gets used up first, and the bonus only becomes active when that's gone. Hit a win while you're still on your own cash, and in most cases you can ditch the bonus and take out your deposit plus winnings with no wagering at all.
Which one's better for you
Non-sticky is usually the better deal, because you keep the choice: walk away with real winnings, or keep going with the bonus. Sticky locks your deposit into the wagering requirement (exigence de mise) from the very first spin.
Real-life example
You deposit 100 $ and get a 100 $ sticky bonus. After wagering, you're at 260 $. You cash out: the 100 $ bonus gets taken off and you receive 160 $.
Now the non-sticky version: say your 100 $ of real money had climbed to 260 $ while the bonus was still untouched. You'd just cancel it and pull out all 260 $.